Draw Reduction Calculator

Compute draw ratios and how many draw/redraw stages a cup needs to form without tearing.

Each draw stage can only reduce the diameter so far before the wall tears. The first draw takes the biggest reduction; redraws take less because the metal has work-hardened.

Calculate the number of stages so each stays within the safe limiting draw ratio for the material.

Formula: Reduction % = (1 − d / D) × 100

Worked Example

  1. Drawing a 4.0 in blank to a 2.4 in cup is a (1 − 2.4/4.0) = 40% reduction — feasible in one draw for many steels.
  2. Going to 1.6 in would be 60% — too much for one hit, so plan a redraw.

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